Hello
You dot need active sonar to plot a good interception course. Use only passive hydrophones.
Do the following:
1) You are submerged and get a contact. Stop the boat and take note of:
a. your course
b. your exact position
c. The bearing.
Note: To determine the exact bearing, move the pointer slowly until u start rearing a faint sound of a ship. Every contact takes 20o. Take the bearing and sum / diminish 10. Doind this, you will find the center of the 20o cone. So, if you start rearing sound at 93, the ship will be at 83degrees. copy?
2) Take new bearings each 10 to 30 minutes, repeat 2 times, so u ll have at the end 3 bearings.
3) Plot them on the navmap.
4) Now start moving at full speed, trying to move to the same side of the ship. I mean... if it goes to starboard, set any course to starboard. If its going east go east. if it goes west go west. You may surface but it can be risky in late war.
5) Leave your ship moving and go to nav map, and draw a circle with the compass.
The circle must have its arrow directed horizontally to any side you want.
6) now, take the proctator. Click in the center and see the horizontal arrow. Now, if the ship is coming from your left, take the protactor's central point to left side of the circle's diameter.
7) Now, before clicking again, take your appointments. Take the difference between the first and the second bearings. I will call it angle "D". Calculate this: (180 - 2D) / 2. With the result of this equationin mind, direct the second extremity of the proctator to below the circle, at an angle = to the ... result of the equation.
8) Take the proctator again and draw another angle from the left side of the diameter of the circle, passing through the center, and direct it to below the circle with the same angle of the equation. Now, you should have a triangle.
9) Repeat these steps to draw another triangle this time within the right side of the diameter, but use the difference of the 2nd and 3th bearings. Now you have two triangles (isosceles triangles).
10) Use compass to draw a circle from the vertices of each triangle to the center of your circle. The new circles should cross themselves in two points: one at the center of the old circle, other in a position we will call "S".
11) Draw an angle from "S" , anchor it on the left side of the old circle's diameter and direct it along the diameter, to right. Get the resulting angle....
12) ...And use it to draw an angle from your first position, to any point in the first
line of bearing, directed to east, just like your target.
13) Now you have its course.
14) After 30 min at full speed, stop th boat and take a new bearing, your new position, and actul course. Draw this new bearing.
15) Observe how the line we called the course of the target, as it crosses the other bearing lines.... intervals are supposed to be equal to each other. Sum This interval along the course line from the 3th bearing line, and you' ll have the 4th bearing, which you would detet if you were still at the first position.
16) Observe the 4th bearing line as it crosses the actual bearing you have plotted from your new position, and you will have its current position. with this in hands, you can calculate the speed.
As it is an approximation, when u have the ship in front of the scope, take a definitive reading of the speed...
It is kinda hard to understand as you see for the first time, but works fine, just be certain to get a consistent bearing variation.
Active sonar gives your position to escorts... i dont like to use. I hope my english is clear enough for you to understand
